The robotic garden tools, such as, but not limited to robotic lawnmowers are widely used for grass cutting applications in a lawn. As these robotic garden tools are autonomous, there is a need that they should have knowledge of the lawn area to be cut along with its boundaries. If the robotic garden tool does not have information regarding the boundaries, it may go beyond the cutting area of the lawn or even may cut undesired areas inside the lawn, like a flower bed.
U.S. Application No. 20070142964 published on Jun. 21, 2007, titled “Robot docking station and robot for use therewith” describes charging apparatus for robot and method for reaching the charging apparatus. Here, the area inside which the mowing operation is being performed is delimited by a boundary wire. Whenever the robotic garden tool needs to replenish its battery supplies it detects the boundary wire and depending on the strength of the signal it comes to know its actual location with respect to the wire. Further, on reaching the wire it follows the wire until the charging apparatus is reached. But a problem with such systems is that the signal from the wire has to be sensed continuously by the robotic garden tool. Hence, the above mentioned system needs a very high power generator for generating the magnetic fields which can be detected from all points inside the working area. Also, the receiver on the robotic garden tool needs to be very sensitive, increasing its cost. Further, in the areas around ferromagnetic materials, the strength of the magnetic field may be reduced or even may get attenuated completely. In such cases the robotic garden tool may stop the operation.
Further, to avoid problems associated with boundary wire, grass sensors may be used. In such systems, the robotic garden tool may operate only on detection that grass surface is beneath the robotic garden tool.
U.S. Application No. 20080039974 published on Feb. 14, 2008 and assigned to iRobot Corporation, titled “Robot Confinement” describes a technique for automated boundary and cutting surface detection. Here, the robotic garden tool detects the grass surface for performing the mowing operation. Here, it also differentiates the actual cutting area form non-cutting grass areas such as flower beds and adjacent grass surfaces by boundary delimiting means. But, if these delimiting means fails, the mower may then fail to distinguish between these areas and may damage these non-cutting areas.
In light of the foregoing, there is a need for an improved method for robotic garden tool for detecting the boundary of the working area and also for differentiating the working and non-working areas inside the lawn area, which can overcome the disadvantages of requirement of high power transmitting signal, complex integration, and difficulty in disambiguation between the working and non-working areas. Further, there also exists a need for providing the robotic garden tool information of its complete working environment, for operating it more efficiently.